What are the natural disasters?

Edit this passage about the China disaster.

China has the largest variety of natural disasters in the world. The National Science and Technology Commission, the State Planning Commission and the Natural Disaster Comprehensive Research Group of the State Economic and Trade Commission classify natural disasters into seven categories: meteorological disasters, marine disasters, flood disasters, geological disasters, earthquake disasters, crop biological disasters, forest biological disasters and forest fires.

Meteorological disaster

There are more than 20 kinds of meteorological disasters, mainly the following: (1) rainstorm: mountain torrents, river flooding and urban water accumulation; (2) Rain and waterlogging: waterlogging; (3) Drought: drought in agriculture, forestry and grassland, and water shortage in industry, cities and rural areas; (4) Dry-hot wind: dry-hot wind and foehn wind; (5) High temperature heat wave: extreme heat and high temperature, human diseases, burns, and crop ripening; (6) Tropical cyclones: gale, rainstorm and flood; (7) Cold damage: crops, livestock and fruit trees are harmed by strong cooling and low temperature; (8) Freezing injury: frost, crop and livestock freezing injury, water pipes and oil pipes freezing injury; (9) Freezing rain: wires, branches and roads are frozen; (10) Freezing: rivers, lakes and seas freeze, and roads freeze after rain and snow; (1 1) Snow damage: snowstorm, snow; (12) Hail disaster: destroying crops and houses; (13) Wind disaster: falling trees, reversing houses, reversing cars and reversing boats; (14) Tornado: local destructive disaster; (15) Lightning: lightning casualties; (16) Continuous rain (acid rain): it is not conducive to crop growth and development, grain mildew, etc. (17) dense fog: human diseases and traffic jams; (18) low-altitude windshear: aviation accident; (19) acid rain: crops are harmed. (20) Sandstorm: death of people and animals, collapse of buildings, reduction of agricultural production, air pollution and loss of topsoil.

Marine disasters

There are mainly the following types of marine disasters: (1) storm surge: including typhoon storm surge and temperate storm surge; (2) Tsunami: There are two types: long-range tsunami and local tsunami; (3) Waves: including wind waves, swells and nearshore waves, which are divided into typhoon waves and cyclone waves; (4) seawater; (5) red tide; (6) Coastal disasters: such as coastal erosion, landslides, land salinization and seawater pollution. (7) the harm of El Nino. (8) The harm of La Nina.

Flood damage

(1) rainstorm disaster; (2) mountain torrents; (3) snowmelt flood; (4) ice flood; (5) dam-break flood; (6) Debris flow and cement flood.

earthquake disaster

(1) tectonic earthquake; (2) Collapse earthquake; (3) mine earthquake; (4) Reservoir earthquake, etc.

Crop biological disasters

(1) Crop diseases: mainly including more than 240 kinds of rice diseases, more than 50 kinds of wheat diseases, more than 40 kinds of corn diseases, more than 40 kinds of cotton diseases and many diseases such as soybean, peanut and hemp; (2) crop pests; There are mainly 252 kinds of rice pests, more than 0/00 kinds of water wheat pests, 52 kinds of corn pests, more than 300 kinds of cotton pests and various other crop pests. (3) Crop weeds: about 8,000 species; (4) Rat damage.

Forest biological disasters

(1) Forest diseases: 29 18 species; (2) Forest pests: 5020 species; (3) Forest rodents: 160 species.

forest-fire

Forest fire caused by high temperature. There are seven main disasters closely related to daily life:

geologic hazard

Both natural changes and human activities may lead to changes in geological environment or geological body. When this change reaches a certain level, landslides, mudslides, land subsidence, ground collapse, rock swelling, sand liquefaction, land freezing and thawing, soil salinization, land desertification, earthquakes, volcanoes, geothermal disasters and other consequences will do harm to human beings and society. This phenomenon is called geological disaster. Geological disasters also include derivative disasters. (1) Debris flow. Debris flow is a special torrent containing a lot of sediment and stones in the valley under the stimulation of heavy rain and melting of snow and ice. The formation of debris flow: the following three conditions must be met at the same time: steep terrain is convenient for water collection and water collection; Abundant loose matter; There is a lot of water in a short time. The material composition of debris flow can be divided into three categories: debris flow consists of a large number of cohesive soil, sand particles and stones with different particle sizes; Mainly cohesive soil, containing a small amount of clay particles and stones, with high viscosity, which is called mud flow when it becomes thick mud; Water-rock flow consists of water, sand and stones of different sizes. Hazard of debris flow: hazard to residential areas; Harm to roads and railways; Harm to water conservancy and hydropower projects; Damage to mines; (2) landslides. The phenomenon that the rocky mountain on the landslide slides down a weak surface (or weak zone) under the action of gravity for various reasons is called landslide. Commonly known as "walking mountains", "crossing mountains" and "sliding soil". Conditions of landslide: Only when the rock and soil mass of the slope is cut and separated into a continuous state by various structural planes can it have the conditions of downward sliding. The activity intensity of landslide is mainly related to the scale, speed, distance, accumulated potential energy and generated kinetic energy of landslide. Activity time of landslide: it is mainly related to various external factors that induce landslide, such as earthquake, rainfall, freezing and thawing, tsunami, storm surge and human activities. (3) collapse. Collapse, also known as caving, collapse or collapse, is a geological phenomenon in which the rock mass on the steep slope suddenly breaks away from the parent body under the action of gravity and rolls and accumulates at the foot of the slope (or gully rock). According to the composition of collapse, collapse can be divided into two categories: soil and falling rocks. Activity time of collapse: collapse generally occurs during or after heavy rain and long-term continuous rainfall; In the fierce process; During or after the excavation of slope toe; The initial stage of reservoir impoundment and the peak period of rivers; After strong mechanical vibration and big blasting. Regionality of collapse: Southwest China is the main area of collapse distribution in China. (4) Land subsidence. Land subsidence is a crustal deformation phenomenon caused by long-term drought, which reduces the groundwater level and overexploits the groundwater. (5) earthquake. Earthquake is a devastating natural disaster. Earthquakes not only directly cause landslides, ground fissures and house collapses, but also cause secondary disasters such as fires, floods, explosions, landslides, mudslides, the spread of toxic gases and plagues.

Floods and other disasters

(1) Rain and waterlogging. Waterlogging refers to the flood disaster caused by large-scale rainstorm or torrential rain. The river water level rises sharply and floods, which leads to the inundation of farmland, houses, people, livestock and transportation facilities, as well as the waterlogging disaster in low-lying areas where accumulated water is difficult to drain, resulting in crop yield reduction and crop failure. (2) floods. Flood disaster refers to the phenomenon that water flows away from waterways or artificially restricted places, endangering people's lives and property. (3) Ice flood disaster. Ice flood disaster is a phenomenon that the water level of the river rises obviously due to the resistance of ice to the water flow, which leads to disasters. (4) Earthquake disaster. Earthquake flood refers to the flood disaster caused by the earthquake blocking the river or the landslide induced by the dam.

Gale disaster

The wind is strong enough to endanger people's production activities, economic construction and daily life. Hazards of gale: harmful gale mainly refers to typhoon, cold wave gale, thunderstorm gale and tornado. According to the influence of strong wind on agricultural production, it can be summarized as mechanical injury, wind erosion, physiological injury and the influence on agricultural production activities. Among the hazards of strong winds, the destructive power of typhoons is the most prominent.

Tropical cyclone disaster

A tropical cyclone is a cyclonic vortex that occurs in tropical or subtropical oceans. Strong tropical cyclone, accompanied by strong wind, heavy rain, huge waves and storm surges, has a wide range of activities and strong destructive power, and is an important disastrous weather system. China is one of the few countries in the world seriously affected by tropical cyclones.

Hail disaster

Hail is ice or hockey that falls to the ground from strong cumulonimbus clouds. According to the size and damage degree of hail, Kejiangbao is divided into three grades: light hail, medium hail and heavy hail. China is one of the countries suffering from hail disasters in the world. (1) The concept of hail hail is ice or ice hockey that falls to the ground from strong cumulonimbus clouds. (II) Hazards of Hail According to the size and degree of hail, hail hazards are divided into three grades: light hail hazard, medium hail hazard and heavy hail hazard. Hail is very harmful to crops, and China is one of the countries with more hail disasters in the world. (3) The geographical distribution characteristics of hail in China. Hail-prone areas: hail-prone areas in Qinghai-Tibet Plateau, hail-prone areas in the north and hail-prone areas in the south. 2. Less hail areas: The less hail areas in China are mainly distributed in the great plains, deserts and great basin. 3. Temporal distribution characteristics of hail: The season of hail concentration in China is mainly in spring, summer and early autumn. According to the seasonal variation characteristics of hail, it can be divided into the following four types: spring hail, summer hail, late spring and early summer hail, and bimodal hail. There are several types of daily variation of hail: afternoon hail type; Night hail type; Noon hail type; Multimodal types, etc. (4) The intensity characteristics, size, size and weight of hail, duration and accumulated thickness of hail. (5) Prediction and prevention of hail 1. Hail is an unpredictable and disastrous weather. The meteorological station uses a large number of real-time meteorological information such as weather radar, meteorological satellite monitoring and weather map to track and extrapolate the hail weather. People also have a lot of forecasting experience, such as "more hail in dry years", "more steep winds in spring and more hail in summer", "pagoda-shaped dark clouds, red clouds below, hail in front" and so on. To sum up, there are six forecasting methods: (1) feeling hot and cold; (2) Identify the wind direction as "no east wind, no tide, no south wind and no hail"; (3) Look at the cloud color; (4) listen to thunder; (5) Know lightning; (6) View the object. 2. Hail prevention: (1) avoid hail; (2) hail suppression; (3) hail resistance; (4) Hail suppression and hail avoidance can be done by ordinary people, and the latter three items need special departments and personnel. Now with the progress of technology, artificial hail suppression has achieved good results. 3. How to deal with hail: (1) After knowing the weather forecast about hail, people, animals and outdoor articles should be moved to safety. (2) Try not to go out when the hail comes, and pay attention to protect your head and face when you have to go out. (3) If you are outdoors when the hail comes, you should immediately find a place to hide, preferably a solid building. (4) If you are driving or in a car, you should immediately park your car in a place where you can avoid it, and you must not rush forward to avoid unnecessary injuries. (5) Sometimes hail will be accompanied by storms, so special attention should be paid to prevention and avoidance.

Marine disasters

(1) storm surge. The interaction between cold air from high latitudes and tropical cyclones from the sea leads to the occurrence of strong winds and huge waves along the coast, thus forming storm surges. The western Pacific is the area that produces the most storm surges. Storm surge type: typhoon type; Cold high pressure combined with cyclone type in the Yellow Sea and Bohai Sea; Transverse cold and high pressure type; Strongly isolated yellow sea and Bohai sea cyclone type; Strong Mongolian low pressure type; Spatial distribution of storm surge disasters. Storm surges in China are all over the coast, but the main concentrated areas from north to south are: Laizhou Bay; Jiangsu Xiaoyanghekou to Zhejiang Dehaimen; Wenzhou, Taizhou, Shacheng to Minjiang Estuary; Shantou, Guangdong to the Pearl River Estuary; The east coast of Leizhou Peninsula and the northeast coast of Hainan Island. (2) disastrous waves. Waves that cause disasters at sea are called disastrous waves. Formation of disastrous waves: caused by typhoon, temperate cyclone, cold wave and other weather systems and formed by strong winds. According to the type of weather system, disastrous waves are cold and high pressure (also called cold wave type); Typhoon type; Cyclone type; Cold high pressure combined with cyclone. (3) sea ice. Sea ice is formed by harmful water freezing, including river ice and icebergs flowing into the ocean. Sea ice is one of the outstanding marine disasters in polar oceans and some high latitudes. Disaster caused by sea ice. Pushing down offshore oil platforms, damaging offshore engineering facilities and waterway facilities, or colliding with ships, causing major shipwrecks; Obstruct the navigation of the ship, damage the propeller or hull, and implement its loss of navigation ability. Sea ice blocks the harbor, which leads to the normal operation of the port or greatly increases the cost of using icebreakers to break ice and pilot; The fishing moratorium is too long, and fishery facilities and places are destroyed, resulting in economic losses. The main characteristics of sea ice disasters are the Bohai Sea, the northern Yellow Sea and the coastal waters of Liaodong Peninsula, as well as some bays of Shandong Peninsula, which are easy to freeze in winter in China. (4) Tsunami. Tsunamis are mainly marine disasters caused by severe earthquakes in countries along the Pacific Ocean. Conditions for tsunami formation: the focal point of the submarine earthquake that caused the tsunami is shallow, generally less than 20 km to 50 km; The magnitude is generally above 6.5 on the Richter scale; There must be a large-scale vertical movement on the seabed; The sea area where submarine earthquakes occur must have a certain depth, especially the transoceanic tsunami, which is generally above 1000 meters. Hazards of Tsunami: The form of tsunami in coastal areas is the sudden rise of seawater, which suddenly forms a "water wall" marching towards the shore. With the rumbling noise, it instantly invades coastal land, engulfs fertile fields, towns and villages, and then the seawater suddenly recedes, or rises first and retreats, and sometimes appears repeatedly, causing huge losses to human life and property. (5) Red tide. Concept of red tide: Red tide refers to the phenomenon that some tiny phytoplankton, protozoa or bacteria suddenly increase in seawater under certain environmental conditions, and the seawater becomes discolored within a certain range for a period of time. Harm of red tide: causing marine variation, partially interrupting the marine food chain and threatening the survival of marine life; Some red tide organisms excrete or decompose mucus after death, which makes marine animals filter food and breathe, thus suffocating them. Or the toxins contained in red tide organisms are ingested by marine animals, resulting in poisoning and death of fish, shrimp and shellfish. Some will poison vertebrates and humans after eating; In the following sections, we will introduce several common natural disasters with large destruction areas, and also introduce some disaster prevention and relief measures.

Other disasters

In addition to earthquakes, floods, typhoons, plagues and other disasters that seriously affect our lives and even threaten our lives, we should constantly raise our awareness and strengthen our ability to prevent other disasters such as lightning, fog and hail. The weather with lightning (1) is called thunderstorm in meteorology. In thunderstorm weather, when the potential difference between clouds and the ground reaches a certain intensity, discharge will occur, and lightning strikes the ground or some objects, which will cause lightning strikes. According to research, the lightning current intensity can usually reach tens of thousands of amperes and the temperature can reach 20,000 degrees Celsius. The harm degree of such a strong current and high temperature can be imagined. (2) lightning protection measures 1. In thunderstorm weather, people should try to stay indoors, don't go out, close doors and windows to prevent lightning from entering the room. 2. Try not to get close to doors and windows, stoves, heaters and other metal parts, and don't stand barefoot in soil or concrete. It's best to sit on a wooden chair with non-conductive items under your feet. Don't swim or row in the river, in case lightning strikes people through the water. 4. When there is a thunderstorm outside the venue, look for low-lying areas or ditches as soon as possible, and don't shelter from the rain under isolated trees, towers and telephone poles. 5, once someone was struck by lightning, should be timely rescue, rescue method is the same as the electric shock first aid, timely artificial respiration and extracorporeal heart massage, etc. And rushed to the hospital at the same time. Anti-fog refers to the fog in which a large number of small water droplets or ice crystal particles are suspended in the low-altitude air, which blurs people's vision and the horizontal energy distance of the parties drops below 1000 meters. Fog classification, when the energy distance is less than 1000m and more than 500m, is called light fog. When the visible distance is less than 500 meters, it is called fog; When the visible distance is less than 200 meters, it is called dense fog. Fog disaster protection measures: 1. Try not to go out. When you have to go out, wear a mask to prevent inhalation of toxic gases. 2. Try to exercise as little as possible in foggy days, and don't exercise in foggy days. 3, pedestrians should be careful when crossing the road, should see the traffic. 4, driving vehicles and cars to slow down, listen to the traffic police command, don't grab a car (boat), when the ferry stops, don't crowd at the ferry. Natural disasters and epidemic natural disasters have destroyed the ecological balance between people and their living environment, and formed the conditions for infectious diseases to spread easily. Therefore, controlling infectious diseases has become an important part of disaster relief work. After natural disasters, with the destruction of the old ecological balance and the establishment of the new balance, the changes in the epidemic conditions of infectious diseases caused by disaster conditions will still exist for some time. The "sequela" of this disaster makes the control of infectious diseases under disaster conditions different from other disaster relief work. When the direct consequences of natural disasters are basically eliminated, eliminating their "after effects" will become the focus of work, and this kind of work will actually become the main work of infectious disease control under disaster conditions.

Edit the disaster impact of this paragraph.

For different types of natural disasters, infectious disease control also has different characteristics. In this sense, disasters can be divided into sudden disasters, including floods, earthquakes, volcanic eruptions, tsunamis, typhoons and other natural disasters that have caused great damage in a short time; Progressive disasters, including drought and famine caused by insect disasters, which are rare now. Because the latter disaster did not have a sudden impact on the basic living conditions of human beings, the prevention and control of infectious diseases can be carried out more unorganized.

Influence on epidemic mechanism of infectious diseases

(1) The drinking water supply system was destroyed. Most natural disasters may cause the destruction of drinking water supply system, which will bear the brunt of the disaster, and often cause the outbreak and epidemic of large-scale intestinal infectious diseases in the early days after the disaster. When a flood occurs, the original safe drinking water source is flooded, destroyed or blocked, and people are forced to use surface water as the main drinking water source. These waters are often polluted by human and animal excreta, human and animal carcasses and dirt in damaged buildings in the upper reaches, especially in low-lying waterlogged areas, where the victims have been besieged by floods for a long time and even caused the outbreak of water-borne diseases. During the floods in Bangladesh, a large number of people died. During the earthquake, the destruction of buildings will also involve the water supply system, which will interrupt the normal water supply of residents and have a serious impact on urban residents. The remaining water sources are also easily polluted due to the destruction of pipelines. Tsunamis and storms may also lead to this situation. During the disaster, many drinking water sources dried up, leading to the concentration of drinking water sources. In some water-deficient areas prone to disasters, residents often need to go far away to get drinking water. Once these water sources are polluted, it will cause an outbreak of disease. For example, Batang, Sichuan, once had a very serious epidemic of bacillary dysentery due to drought. In some low-lying saline-alkali areas, floods and droughts will also change the groundwater level, thus affecting the salt content and PH value of drinking water. When the PH value and salt content in water increase, it is beneficial to the reproduction of Vibrio cholerae. Therefore, in some cholera epidemic areas, cholera often recurs due to floods and droughts, and it can last for a long time. (2) Food Shortage Although delivering food to the disaster area has become the first task of disaster relief, it is still difficult to completely avoid local food when a large-scale natural disaster involving a large area occurs. Coupled with the destruction of basic living conditions, people are forced to store food under harsh conditions, which can easily lead to food mildew and corruption, food poisoning and the prevalence of food-borne intestinal infectious diseases. Floods are often accompanied by rainy weather, when food is easy to get moldy. Recently, during the large-scale floods in several southern provinces of China, many incidents of mold poisoning occurred. When disasters occur in hot weather season, food is prone to spoilage. Because pickled food is easy to preserve, it often becomes the only non-staple food for residents when the supply of non-staple food is interrupted in large-scale disasters, which also provides conditions for halophilic bacteria poisoning. Food shortage will also lead to a general decline in people's physique, thus making various diseases prone to occur and epidemic. (3) Fuel shortage In large-scale natural disasters, fuel shortage is also a common phenomenon, especially among victims trapped by floods. Fuel shortage first forced the victims and raw water to eat cold food, which led to the occurrence and spread of intestinal pollution. When it is difficult to restore fuel supply in a short time after a serious natural disaster, fuel shortage may lead to a decline in the personal hygiene level of residents. Especially in winter, people still live in a crowded state, which may lead to the breeding and spread of parasites on the body surface, which may lead to the resurgence of some infectious diseases that have been controlled, such as epidemic spot and typhoid fever. (4) Water pollution floods often cause water pollution, leading to a large-scale epidemic of some water-borne infectious diseases, such as schistosomiasis and leptospirosis. But the impact of flood on water pollution is twofold. In large-scale floods, especially during travel, due to the dilution of floods, the incidence of such diseases shows no obvious signs of rising. However, when the flood began to fall, many small bodies of water were left in the waterlogged area. If these small water bodies are polluted, it will easily lead to the outbreak and epidemic of such diseases. (5) Destruction of living conditions Floods, earthquakes, volcanic eruptions and tsunamis will cause large-scale destruction of living conditions. At first, people are forced to sleep outdoors, and then they may live in simple shacks for a long time, resulting in concentrated population and crowded living. During the Tangshan earthquake, in Tangshan, Tianjin and other big cities, simple shacks stretched for dozens of miles, and the longest lived for more than a year. Even after moving back to the original residence, due to the destruction of a large number of houses, some residential congestion will continue for a long time. Sleeping outdoors makes people vulnerable to attack by blood-sucking arthropods. At this stage, the incidence of insect-borne infectious diseases may increase, such as malaria, Japanese encephalitis and epidemic hemorrhagic fever. The crowded population is conducive to the prevalence of some diseases spread through close contact between people, such as hepatitis and pinkeye. If this situation continues into winter, respiratory infectious diseases, such as influenza and epidemic cerebrospinal meningitis, will become a serious problem. (6) Population Migration Natural disasters often cause large-scale population migration. During the Tangshan earthquake, the wounded were directly transported to Chengdu and Chongqing in the southwest hinterland of China. During the period of urban reconstruction, people evacuated in the form of relatives and friends almost spread all over China. Nowadays, under the current economic conditions, going out to engage in labor activities has almost become the most important form of self-help activities for residents in disaster areas. The large-scale migration of population first created conditions for the spread of some endemic diseases, and led to some diseases becoming epidemics, such as the Black Death in the Middle Ages. The latest plague epidemic in the history of China and Yunnan began with population movement. Population mobility has caused two problems. First, when the population in the disaster area flows out, it may spread the endemic diseases in the disaster area to the disaster-stricken areas. More importantly, when the disaster area begins to rebuild and the population returns home one after another, endemic diseases and infectious diseases will be brought back to the disaster area. If the disaster area has the conditions for epidemic diseases, it may create new epidemic areas. The second major problem of population mobility is that it interferes with the immune status of some people who mainly rely on immunity to control diseases, resulting in local non-immune people, thus creating conditions for the prevalence of these diseases. In China, planned immunization has been widely carried out, and great achievements have been made in controlling polio and measles. The incidence of typhoid fever, tuberculosis, hepatitis A and hepatitis B began to decline. Due to the interference of disasters, it is difficult to carry out planned immunization work normally, and some children miss vaccination due to abortion, which may increase the incidence of such diseases. Some diseases that often occur among children and young people, as well as diseases in the natural immune state of the population, play an important role in the epidemic. No matter the outflow of people from the disaster area or the return of people during the reconstruction of the disaster area, some non-immune people will come into contact with the low-level natural epidemic population, which will lead to an increase in the incidence of these diseases.

Influence of biological vectors of infectious diseases

Many infectious diseases not only spread from person to person, but also have other biological hosts besides people. Some diseases must be transmitted through biological media. Disaster conditions have destroyed the old ecological balance among human beings, host animals, biological media and disease pathogens, and will establish a new ecological balance on a new basis. So the impact of disasters on these diseases will be more lasting. (1) Flies are important vectors of intestinal infectious diseases, and their breeding and reproduction are mainly determined by the unsanitary living environment of human beings. Major natural disasters will always cause great damage to the sanitary conditions of human living environment, and the breeding of flies is almost inevitable. After the earthquake, the house collapsed. Buried under the ruins are the bodies of dead people and animals, as well as a lot of things and other organic substances. Under the climatic conditions of temperature, these organic components will rot rapidly, which provides conditions for flies to reproduce easily. Therefore, earthquake damage as large as Tangshan earthquake often causes a surprising number of adult flies in a very short time, posing a serious threat to the residents in the disaster area. After the flood recedes, drowned animal carcasses and all kinds of organic garbage will be largely silent in the ruins of the old village, and if they are not removed in time, a large number of flies will also breed. Even in the case of drought, due to lack of water, there will be some unsanitary conditions, which is conducive to the breeding of flies. Therefore, in the early stage of post-disaster reconstruction, eliminating flies will become an important task of infectious disease control. (2) Among the blood-sucking arthropods that spread diseases, mosquitoes are the most important and have the closest relationship with disasters. Under the common disaster conditions in China, malaria and Japanese encephalitis are the most serious threats to the residents in the disaster areas. Mosquitoes need a small and still water body to breed. Therefore, in flood water, the increase of mosquito density is often not obvious during flood discharge. However, after the water recedes, a large number of small waterlogged areas often appear in the low-lying areas of waterlogged areas, which are overgrown with weeds and become the best breeding grounds for mosquitoes. At this time, if there is a source of infection, the incidence in this area will increase rapidly. Drought will cut off some rivers and dry up lakes, and the small puddles left in these rivers and lakes will also become good breeding grounds for mosquitoes. In earthquakes, wind disasters and other disasters that cause a lot of damage to buildings, water storage buildings and pipelines may be damaged at the same time. The overflow of tap water, especially domestic sewage stranded on the ground, will also become an environment for mosquitoes to multiply. Disasters will not only increase the density of mosquitoes, but also increase the chances of mosquitoes attacking humans. Residents trapped by floods and forced to sleep outdoors due to the destruction of houses often lack effective means to resist mosquito invasion, which is also an important reason for the increase in the incidence of mosquito-borne diseases. (3) Under disaster conditions, other blood-sucking arthropods mainly show that the probability of blood-sucking arthropods attacking humans increases, and mosquitoes sometimes mechanically spread some rare infectious diseases such as anthrax. People who sleep in places rich in weeds and humus are vulnerable to chigger mites and gamasid mites. In areas with tsutsugamushi disease and epidemic hemorrhagic fever, this threat to human beings has greatly increased. Disasters in forest areas, such as forest fires, will increase the chances of tick bites and may lead to a series of diseases such as forest encephalitis, Lyme disease and spotted fever. (4) Parasites In China, the distribution of schistosomiasis is mostly in some flood-prone areas, and the distribution of snails is greatly affected by floods. In normal times, the distribution of Oncomelania hupensis constantly changes with the scouring of water and the formation of shoals. Under flood conditions, it is possible to take snails away from their original breeding grounds and settle down in a new and suitable environment. Therefore, floods often significantly expand the distribution area of schistosomiasis. (5) Domestic animals are important hosts of many infectious diseases, such as pigs and dogs are hosts of leptospirosis, pigs and horses are hosts of Japanese encephalitis, and cattle are hosts of schistosomiasis. When a flood disaster occurs, a large number of victims and livestock are often trapped in their narrow areas by floods. The natural return to the sea has caused great damage to houses, and it will also lead to an unusually close relationship between people and livestock. This environment will make it easy for people and animals to spread infectious diseases. (6) Domestic and wild rodents Domestic and wild rodents are the most important disease hosts, and their distribution and density are obviously affected by natural disasters. Most rodents related to diseases live in underground caves, and their swimming ability is not very strong. Therefore, when a large-scale flood occurs, the number of rodents will decrease. However, some rodents may use floating objects to escape and concentrate in the higher places where the victims live, thus forming an unusually high density in some areas. In this case, due to the close contact between humans and rodents, it is possible to cause the epidemic of diseases. Because of the strong reproductive ability of rodents, they usually leave abundant food for rodents in villages and farmland damaged by floods. Therefore, after the flood recedes, the density of rodents may rise rapidly, and a very high population density will appear for a period of time thereafter, thus promoting the epidemic of infectious diseases and endangering human beings. Drought may dry up some lakes and swamps and turn them into overgrown lowlands. This area provides a superior living environment for wild rodents, which makes their number increase sharply. It is reported that this situation leads to epidemic hemorrhagic fever in the population.